A driving circuit used by LED head includes a LED driving and outputting section (hereinafter: LED driving and outputting circuit) to individually drive LED elements. A conventional LED driving and outputting circuit is constructed from a series connection of first and second PMOS transistors. A control voltage corresponding to a drive electric current value is supplied to gate of the first PMOS transistor, and a drive ON/OFF instruction signal is inputted to gate of the second PMOS transistor.
As stated in the a patent document 1 of Japan patent publication Hei 11-291550 and a patent document 2 of Japan patent publication 2001-056669, in the conventional LED driving and outputting circuit, because the control voltage corresponding to a drive electric current value is always supplied to the gate of the first PMOS transistor, its drain is kept by a voltage which is approximately equal to a power source voltage. Thereby, when a drive ON instruction signal is inputted to the gate of the second PMOS transistor in order to drive LED element to turn on, with the second PMOS transistor becomes ON, electric charge that keeps the drain in the voltage approximately equal to a power source voltage is discharged via the second PMOS transistor and LED element without any electric current control. As a result, when electric current that flows through LED element rises, peak electric current flows sharp. Because of the excessive peak electric current, the LED element degrades and its life becomes short.